Keep Only the Highest Set Bit

Code

#include <stdio.h>
#include <stdint.h>

// Complete the function
uint16_t highest_set_bit(uint16_t reg) {
    if (reg == 0) return 0;  // Special case: if reg is 0, return 0

    // Step 1: Propagate the highest set bit to the right
    reg |= reg >> 1;  // Spread the highest set bit to the right
    reg |= reg >> 2;  // Continue spreading
    reg |= reg >> 4;  // Continue spreading
    reg |= reg >> 8;  // Continue spreading

    // Step 2: Isolate the highest set bit
    return (reg + 1) >> 1;  // Add 1, then shift right to isolate the highest set bit
}

int main() {
    uint16_t reg;
    scanf("%hu", &reg);
    uint16_t result = highest_set_bit(reg);
    printf("%hu", result);
    return 0;
}

Solving Approach